With the trend toward further size-reduction in the fields of semiconductors, micro electro mechanical systems (MEMS), etc., a technology in which an existing photolithographic technique is combined with a fine processing technique of shaping a resist (photocurable composition) on a substrate (wafer) by using a mold so as to form a resist pattern on the substrate has drawn much attention. This technology is also called a photo imprint technology and can be used to form sub-ten-nanometer order fine structures on a substrate. In a photo imprint system, a resist is first applied to a pattern-forming region of a substrate and then this resist is shaped by using a mold on which a pattern has been formed. Then light is applied to cure the resist and the mold is separated. As a result, a resin pattern (photocured product) remains on the substrate.
When forming the resin pattern (photocured product), the thickness of a residual film of the resin pattern (photocured product) is desirably uniform across the surface of the substrate. This is to suppress in-plane line-width variation that occurs, for example, as a result of dry etching in an etching step, which is a step in the semiconductor device production process other than the pattern-forming step in which the imprint system is used. PTL 1 discloses an imprint method that, in applying a resist onto a substrate by an ink jet method, optimizes the arrangement of resist droplets according to the density of a pattern to be transferred. However, according to this imprint method in which the resist is arranged on a substrate in a discrete manner, the resist does not easily spread on the substrate and thus at the time of pressing a pattern portion of a mold against the resist on the substrate, bubbles tend to remain between the pattern portion and the resist. If the resist is cured with bubbles remaining therein, the resulting resin pattern (photocured product) may come to have an unintended shape. However, productivity would be impaired if one were to wait until the remaining bubbles disappeared.
PTL 2 discloses a method of introducing a condensable gas, which becomes condensed under capillary pressure generated as the resist penetrates the gap between the substrate and the mold and recesses on the mold, between a mold and a substrate so that the gas condenses and undergoes volume reduction after introduction of the gas and that bubbles disappear more rapidly. The condensable gas used in PTL 2 is trichlorofluoromethane (CFCl3). NPL 1 describes that the filling property is improved by using 1,1,1,3,3-pentafluoropropane (CHF2CH2CF3) as the condensable gas.
However, these processes that use a condensable gas roughen the surface of the resist although the filling time is shortened.